Velocity modulation tube



' March 3, 19,53

J. R. WOODYARD EI'AL VELOCITY MODULATION TUBE Original Filed Dec. 7, 1942 @w i 1.7 B

INVEN-rons J. R. wooo YARD w. w. HANSEN ATTORNEY Patented Mar. 3, 1953 VELOCITY MODULATION TUBE John R. Woodyard, Berkeley, and William W. Hansen, Stanford University, Calif., assignors to The Sperry Corporation, a corporation of Delaware Original application December 7, 1942, Serial No.

'7 Claims.

This invention relates to ultra-high frequency apparatus and more particularly to space resonaftor devices having special arrangements for direction and velocity modulation of an electron stream.

The invention will be described in its embodiment with electronic devices of the type wherein an electron beam is velocity modulated due to passage through a high frequency electric iield produced by a hollow resonator.

In order to handle large power inputs and out puts in such devices it has heretofore been proposed to increase the cathode or current emission area by designing the resonators and associatedgrid structure in the form of figures of revolution about various axes, so that the cathode and grid areas are made relatively large without changing the resonating characteristics. Some of these structures are shown in United States Letters Patent No. 2,259,690 in which we arecoinventors.

The present invention is an improvement over the development represented by said patent and is especially directed to velocity l'nodulated` electron beam devices` for high power operation wherein the resonator, grid and cathode structurespreferably comprise figures of revolution in special highly eiiicient association with anew arrangement for passing the electron beam radially inwardly through the resonator field thereby ob-` taining an exceedingly high concentration of electrons within the field of the resonator forl producing large output energy. This application is a division of our Patent No. 2,456,067 for High Frequency Apparatus, issued April 5, 1949.

It is therefore a major object of our invention to` provide an ultra-high frequency device of the velocity modulated electron beam type having novel internal construction and unusually eflicient operational characteristics.

A further object of the invention is to provide a novel high frequency device of the velocity modulation type wherein an annular hollow resonator means is arranged. about an axis and an electron beam is projected transversely inwardly toward that axis through the eld produced by the resonator.

It is a further object of the invention to provide an ultra-high frequency device of the velocity modulated electron beam type having a hollow resonator substantially in the form of a gure of revolution about an axis and an electron beam transversely projected through the fig` ure. Pursuant to this object the electron emitter may be shaped and located so as tosurround Divided and this application January 22, 1949, Serial No. 72,162

the resonator, and the electron stream is generally radially inwardly directed.

A further object of the invention is to provide a high frequency velocity modulation device em bodying a hollow resonator in the form of a gure of revolution about an axis and having novel asscciated grid and reflector arrangements.

'Further objects of the invention will presently appear as the description proceeds in connection with the appended claims and the annexed drawings in which:

Fig. 1 is a perspective sectional view of a reex device having an internal reflector and` embodying the invention; and

Fig. 2 is a View similar to Fig. 1 but employing a differently shaped resonator and having the electron emitter contained within the conines of the resonator.

As will appear in the following detailed description, the device of the invention is primarily designed by developing, preferably by rotation about a selected axis, a generally toroidal structure having the same shape and appearance in cross-section as a simple velocity modulation device and having its grid sections substantially longitudinally disposed in the path of generally transversely or radially directed electrons from an external or internal cathode surface. The development of the figure about the axis is not limited to continuous revolution, such as a circle or ellipse, for example, but may include discontinuous revolution, such as a rectangle, as may be desired. In eifect, theinvention is chiefly cone cerned with what may be designated as a radial electron beam velocity modulation device, as distinguished from the usual velocity modulation devices embodying electron beams directed axially of the hollow resonator.

Referring now to Fig. l of the drawings, the invention is illustrated as comprising a casing l having cylindrical side walls and stepped circular end walls 2. Contained within the casing l] there is an annular hollow cathode element 3 having a relatively large uniform electron emitting surface 4 of annular shape. This cathode element 3 is shown supported by insulating posts :5 from the side walls of the casing l. The cathode is energizedk by a coiled wire filament 6 that is adapted to be heated to incandescenceby energy supplied from a battery 'i through lead 8 and return lead S. Leads "8 and 9 include terminals lll and It extending through glass orlike insulated gas-tight bushings lf2 and it in the side Walls of casing l. The casing i is shown provided with internal partitions It, t4', t5. i5?, t6 and IB 3 which together with the walls of the casing dene an internal cavity resonator Il comprising essentially upper and lower toroidal sections which are interconnected by a relatively narrow annular gap i8 positioned inwardly of and opposite the cathode emitter surface `fi.

The annular gap I8 is dened by two annular grid structures I9 and 29 having their upper and lower ends secured to the partitions I il, I4' and I5, I respectively. Positioned radially inwardly of the inner grid 28 and spaced therefrom, is an annular reector plate 22 shown supported by insulating rods 23 from the partition I5. Reflector plate or electrode 22 is connected by a lead 24 to the battery 'I through lead 9. An accelerating voltage battery 25 has its low potential side connected to the battery 7 and its high potential side connected to the casing I. An energy eX- tracting loop 25 is shown connected to a concentric line 2'! for removing energy from' the resonator I'I.

In operation, the filament 6 heats the cathode 3 causing electrons to be emitted from the large annular surface i of the cathode and the accelerating voltage supplied from battery 25 to the grid I9 serves to drive these electrons with large energy towards and through the gap I8 of the resonator I'I within which gap the electrons are velocity modulated and then pass from this gap through the grid 2G toward the reflector plate 22. This reflector plate 22, being at a low potential, serves to reflect the electrons in the manner taught in Patent No. 2,250,511 of William W. Hansen and Russell H. Varian, which electrons reenter the gap I8 in groups after passing through grid 2li thereby giving up energy to the reector ITI, which energy is extracted by the loop 26 and concentric line terminal 2l.

Owing to the relatively large area of the cathode emitting surface 4 and to the fact that the gap I8V is of lesser area, a high concentration of electrons enter the gap I8 and after being grouped by the action of reflector 22, reenter the gap so that the device of the present invention is capable of producing relatively tremendous power.

The form of the invention shown in Fig. 2 is similar to that of Fig. 1 except that the resonator I'I has its annular gap I8 positioned inwardly thereof instead of outwardly, as shown in Fig. l,

and the cathode element 3 is wholly contained within the coniines of the casing I. The reflector electrode 22 in this form' of the invention is shown centrally positioned inwardly of the partitions 36, 36 and are similar to partitions It and I6 of Fig. 1.

Other parts of the Fig. 2 similar to Fig. 1 are similarly numbered with primes added.

The operation of the device of Fig. 2 is similar to that of Fig. 1 except the structure is somewhat more compact than that shown in Fig. 1.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departure from' the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. An ultra-high frequency tube of the velocity modulation type comprising a cylindrical casing containing therewithin a single annular resonator having upper and lower tcroidal portions and a connecting annular gap, an annular cathode` Cil positioned radially exteriorly of said annular gap for directing electrons radially inwardly and through said gap and outside said resonator and an annular reector electrode located radially inwardly of said gap for reilecting said electrons back into the same, the large area of said cathode serving to produce a high concentration of electrons passing through said gap in use.

2. In an ultra-high frequency device of the velocity modulation type, hollow resonator means in the general form of a casing constituting a gure of revolution having inner and outer portions enclosing a single cavity, said inner and outer portions having openings therethrough and providing an annular gap therebetween in substantial alignment transversely of the axis of said gure and a surrounding cathode of relatively large area for directing a stream of electrons radially inwardly through said openings and said cavity gap and an annular reflector electrode located radially inwardly of said gap and outside said resonator for reflecting said electrons back into the same.

3. A high frequency apparatus comprising a casing containing a single annular resonator having upper and lower sections and a connecting gap section, said gap section having perforated walls, an annular electron emitter surrounding said resonator gap section for directing electrons radially inwardly thereof for concentration in said gap section and an annular reflector electrode located radially inwardly of said gap section and outside said resonator for reflecting electrons back thereinto, said emitter having a relatively large emitting surface larger than said gap for aiding in concentrating electrons within said gap section.

4. An electrical discharge device comprising a chamber having conducting walls in the form of an outer cylinder having an annular band of perforations in its wall and an inner cylinder interconnected at each end by electrically conducting material, an electron emissive source positioned adjacent t0 said perforations and insulated from said walls, means included by said device for impressing an electric field in the region adjacent said source for projecting electrons from said source through said perforations into said chamber, and coupling means having a portion projecting within said chamber for transmitting energy resident in an electric eld inside said chamber to a work circuit.

5. An electrical discharge device comprising a chamber having conducting walls in the form of an outer cylinder having an annular band of perforations in its wall and an inner cylinder interconnected at each end by electrically conducting material, an electron emissive source, positioned adjacent to said perforations and insulated from said chamber, a vacuum-tight enclosure maintained at a high vacuum enclosing said source and said perforations, and means included by said device for impressing an electric eld in the region adjacent said source for projecting electrons from said source through said perforations into said chamber.

6. An electrical discharge device comprising a chamber having conducting walls in the form of an outer cylinder having a perforated area in its wall and an inner cylinder interconnected at each end by electrically conducting material, said area subtending a major portion of the circumference of said outer cylinder, a linearly extending electron emitter subtending said 5 perforated area, means included by said device for impressing an electric field in the region adjacent said source for causing electrons from said source to be projected through said perforations into said chamber, and means having a portion projecting within said chamber for utilizing the energy of electrical oscillations produced within said chamber.

7. An electron disch-arge device having means including a cathode of annular shape for directing va stream of electrons radially toward the axis of said cathode, an electrode positioned at the @axis of said cathode, and an annularly shaped cavity resonator positioned between said cathode and said electrode, said cavity resonator comprising a pair of comparatively thick ringlike members spaced axially and each having an annular recess adjacent the path of the stream of electrons and a ring-like element ex- 6 rtending over each recess to form therewith a cavity resonator, the edge of said thick ringlike member and edge of the ring-like element providing a gap past which electrons are directed toward the electrode at said axis.

JOHN R. WOODYARD. WILLIAM W. HANSEN.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS- Number Name Date 2,170,219 Seiler Aug. 22, 1939 2,259,690 Hansen et al Oct. 21, 1941 2,372,213 Litton Mar. 27, 1945 2,402,983 Brown July 2, 1946 2,409,694 Laidig Oct. 22, 1946 

